Friedrich Staphylus (27 August 1512 – 5 March 1564) was a German theologian, at first a Protestant and then a Catholic convert.
Staphylus was born at Osnabrück. His father, Ludeke Stapellage, was an official of the Bishop of Osnabrück. Left an orphan at an early age he came under the care of an uncle at Danzig, then went to Lithuania and studied at Cracow, after which he studied theology and philosophy at Padua.
About 1536 he went to Wittenberg, obtained the Degree of magister artium in 1541 and at Melanchthon's recommendation became a tutor in the family of the Count of Eberstein. In 1546 Duke Albert of Prussia appointed Staphylus professor of theology at the new University of Königsberg, which the duke had founded in 1544.
At this time Staphylus was still under the influence of Martin Luther's opinions, as is shown by his academic disputation upon the doctrine of justification, "De justificationis articulo". However, at his installation as professor he obtained the assurance that he need not remain if the duke tolerated errors which "might be contrary to the Holy Scriptures and the primitivœ apostolicœ et catholicœ ecclesiœ consensum". This shows that even then he regarded with suspicion the development of Protestantism.
At Königsberg he had a violent theological dispute with Wilhelm Gnapheus. In 1547-48 he was the first rector elected by the university, but in 1548 he resigned his professorship, because he met with enmity, and was dissatisfied with religious conditions in Prussia. Still he continued to be one of the councillors of the duke. In 1549 he married at Breslau the daughter of John Hess, a reformer of that place.